I had the same problem. You need to uninstall the Picoscope software, and re-install, but this time right click on the installer program and select 'Run As Administrator' (or change the installer filename to include the word 'setup' or 'install')

Existing software for the majority of products will work with Windows Vista as long as the user is logged in as an Administrator. Exceptions include Enviromon and PicoScope 3223, 3224, 3423 and 3424. Help files are not compatible.

In the next software release in March all products will be compatible including PicoLog and PicoScope help files. Not compatible will be the Enviromon help files and product specific help files which will be updated in subsequent releases.